The only way I get a smooth pin surface without any facets or rough edges is to buff the pin after I'm done hammering. Yes, a polished hammer head will help, as will a polished anvil top, but buffing can more than make up for both (and other factors that cause imperfections). I would go so far as to say no matter what your hammer and anvil look like, you'll never get a smooth surface if you don't buff (or sand, or burnish, or whatever).

If you don't have access to a buffer, get some thin brass sheet, drill out a hole to whatever size you need, and play with sanding/steel wool/whatever you have to get a nice, smooth dome. And if you polish the washers in the process, I'd say that's an added bonus.